Context-free and stationary languagest#x2020;

摘要

A stationary word of a OL systemG=(X,P,w) is a word that generates itself after a positive number of direct derivations. The stationary set ofGis the set of stationary words ofGand the stationary language ofGis the set of the stationary words generated byw. The stationary set ofGis a submonoid ofX*containing the adult set ofG.